1. Field of the Invention
The present invention relates to a laminated balance-unbalance converter including a multilayer body, and more specifically relates to a balance-unbalance converter including a low pass filter and a high pass filter within a multilayer body, and is small-sized and in which inductance values of an inductor of the low pass filter and an inductor of the high pass filter are relatively high and magnetic coupling between the inductor of the low pass filter and the inductor of the high pass filter is significantly reduced or prevented.
2. Description of the Related Art
Japanese Unexamined Patent Application Publication No. 2012-205195 discloses a laminated balance-unbalance converter (laminated balun) in which a low pass filter and a high pass filter are formed within a multilayer body in which a plurality of insulating layers are laminated.
In the balance-unbalance converter disclosed in Japanese Unexamined Patent Application Publication No. 2012-205195, the low pass filter includes an inductor and a capacitor and is connected between an unbalanced terminal and a first balanced terminal. In addition, the high pass filter includes an inductor and a capacitor and is connected between the unbalanced terminal and a second balanced terminal.
The balance-unbalance converter disclosed in Japanese Unexamined Patent Application Publication No. 2012-205195 is used at a high frequency such as the 2.4 GHz band, as is seen from a characteristics diagram or the like. Although a frequency being high or low is relative, for example, the 2.4 GHz band is referred to as high frequencies and the 700 MHz band is referred to as low frequencies in the present specification.
It is possible to design the balance-unbalance converter used at a high frequency, such that the inductance values of the inductor of the low pass filter and the inductor of the high pass filter are relatively low.
Meanwhile, from manufactures and sellers of electronic devices in which a balance-unbalance converter is used, there is a large demand also for a balance-unbalance converter used at a low frequency such as the 700 MHz band.
In order to obtain desired characteristics, a balance-unbalance converter used at a low frequency needs to be designed such that the inductance values of the inductor of the low pass filter and the inductor of the high pass filter are relatively high.
In the balance-unbalance converter, in order to make the inductance values of the inductors of the low pass filter and the high pass filter high, for example, it is necessary to increase the length of each inductor. In order to increase the length of each inductor, it is necessary to increase the number of the insulating layers of the multilayer body, increase the planar size of the multilayer body, or achieve both.
However, increasing the number of the insulating layers of the multilayer body to increase the height of the multilayer body or increasing the planar size of the multilayer body is contrary to the demand to reduce the size and the weight of an electronic component.